Spindle assembly with labyrinth seals and hub/back iron spacers

ABSTRACT

A disk drive assembly includes a disk pack with an axially retractable spindle assembly and a rotary actuator, mounted within a unitary deck and precision aligned by bores through spaced apart upper and lower support walls of the deck. Bushing sleeves, mounted through bearings to opposite ends of a spindle shaft, are aligned and secured within the bores by screws through the support walls and threaded into the bushing sleeves, thus to secure the spindle shaft for rotation relative to the support walls. A cup-shaped hub is fixed to the spindle shaft. A radially outward wall of the hub has upwardly converging flutes that cooperate with openings through annular spacers between adjacent disks on the hub, to provide a purging and cooling air flow. The hub and bushing sleeves have interacting pairs of annular flanges and annular grooves, and the bushing sleeves include extensions adjacent the bearings, to control radially outward passage of air from the center of the spindle assembly toward the region of the disks. Three angularly spaced apart fasteners extend through the hub and into an annular back iron through an annular edge of the back iron, to secure the back iron to the hub. An outer circumferential surface of the back iron and the radially outward wall of the hub are radially spaced apart from one another when the hub and back iron are secured. Three spacers between the back iron edge and hub, one surrounding each fastener, maintain the hub and back iron in axially spaced apart relation.

This is a continuation of copending application Ser. No. 07/926,478filed Aug. 28, 1992, now abandoned which is a divisional of applicationSer. No. 07/560,747 filed Jul. 31, 1990.

BACKGROUND OF THE INVENTION

The present invention relates to apparatus for reading, writing andstoring bit-encoded data, and more particularly to disk drives includingpacks of multiple, concentrically stacked disks.

The continuing effort to increase data storage capacities of magneticdisk drives and other data storage devices is concerned largely withincreasing the density at which data can be stored on the availablerecording surface area. Another approach involves mounting multiplemagnetic disks on a single spindle assembly in which the disks arestacked in integral, spaced apart and concentric relation. Such spindleassemblies typically include an elongate shaft, a hub fixed to the shaftand supporting the disks, and bearings and bushings at opposed ends ofthe shaft, to support the shaft, hub and disks for rotation relative tothe disk drive housing. Also mounted movably with respect to the housingis an actuator, either of the rotary or linear type, for selectivelypositioning data transducing heads relative to the disks.

The design and manufacture of such drives involve disparate and oftencompeting needs. The preferred high data storage densities requireprecision alignment of the disk pack and actuator, stability duringrotation of the spindle assembly and resistance to thermal effects dueto differing thermal expansion coefficients of materials employed in thedrive. The housing must be strong, lightweight, resistant to vibrationand provide an effective seal to prevent contamination of the housinginterior, particularly in the region of the disks. At the same time,cost considerations stimulate efforts to reduce the number of parts andsteps involved in assembling disk drives.

Among the many approaches for meeting these needs is a divided housingfor magnetic disks disclosed in U.S. Pat. No. 4,899,237 (Tochiyama etal). The housing includes a shell which supports both a magnetic diskpack and a rotary actuator, and a cover that closes an opening in theshell. Holes that support bushings at opposite ends of the spindle shaftare drilled through opposite side walls of the shell in a singleoperation, 10 and thus are precision aligned. The rotary actuator has ashaft which is similarly mounted by precision aligned holes in theshell. This arrangement is said to enhance the mechanical rigidity ofthe disk pack and actuator mountings, and improve sealing.

U.S. Pat. No. 4,835,637 (Mach et al) discloses a disk file in which adisk stack sub-assembly is mounted within a housing. A shaft of thesub-assembly is mounted to the housing through upper and lower bearingsand associated upper and lower bearing supports. The lower bearingsupport is movable axially with respect to the outer race of the lowerbearing. A spring biases the lower bearing support axially upwardrelative to the lower bearing outer race. This arrangement enablesreduction of the sub-assembly length to enable its insertion betweenopposed parallel walls of the disk file housing.

While the above approaches have met with limited success, there remainsa need to provide a disk drive capable of storing data at relativelyhigh densities, and at low cost.

Therefore, it is an object of the present invention to provide a diskdrive housing which is strong, lightweight and resistant to vibrationand thermal effects.

Another object is to provide a spindle assembly for a disk driveincluding means for mounting a spindle shaft for rotation relative to adisk drive housing, which means are particularly well suited tofacilitate assembly into a unitary housing.

A further object of the invention is to provide, in a spindle assemblywith an internal motor, an effective system for purging air in theregion of disks, and seal against contamination of the region of thedisks from particulates generated near the motor and bearings.

Yet another object of the invention is to provide a mounting interfacefor a spindle assembly and disk drive housing, in which a rotatablespindle shaft is precisely aligned as it is installed into the housing,without jigs or other extraneous alignment tooling.

SUMMARY OF THE INVENTION

To achieve these and other objects, there is provided in a data storageapparatus, an enclosure for supporting a data storage disk and spindleassembly for rotation of the disks inside of the enclosure. Theenclosure includes a unitary, substantially rigid deck including firstand second opposed support walls. An intermediate peripheral wall meanscooperates with the support walls to define a substantially enclosedchamber within the deck, with one end of the deck open to allowinsertion of a spindle assembly into the chamber. The spindle assemblyincludes an elongate spindle shaft and first and second bushing meansrotatably mounted to opposite ends of the shaft. First and secondprecision bores are formed in the first and second support walls,respectively and are open to the chamber. Each precision bore conformsto an associated one of the first and second bushing means. This permitsa tight nesting engagement of each of the bushing means into itsassociated bore, the nesting engagement fixing and aligning therotational axis of the spindle shaft relative to the deck, whilesimultaneously securing the spindle shaft rotatably to the deck. Each ofthe support walls, in a region about its associated one of the first andsecond bores, is tapered gradually from a maximum thickness at the rimof the associated bore to a reduced thickness radially remote from thebore.

Preferably a unitary cover is releasably secured to the deck at the openend to enclose the chamber. Third and fourth precision bores can beprovided in the first and second support walls, respectively, forprecision aligning and supporting a rotary actuator shaft in paralleland spaced apart relation to the spindle shaft, inside the chamber.

To further strengthen the enclosure, reinforcing ribs can be formedalong respective exterior surfaces of the support walls. Preferably theribs are formed as two mutually perpendicular series of substantiallyequally spaced apart ribs, to form a "waffle" pattern of repeatingsquares. The ribs are readily formed in the deck and cover by knowncasting techniques, and form a lightweight housing resistant to torqueand bending stresses. The tapered conical wall portions near the spindlebores attenuate vibrations introduced into the deck and cover,minimizing the influence of vibrations upon data reading and recordingoperations. The combination of the tapered conical walls in the spindlearea, and the waffling technique, results in optimum mass, i.e. minimumweight for maximum strength. The lighter weight deck and cover are lesssubject to outside shock and vibration, since the shock mounts havelimited deflections.

Another aspect of the present invention is a spindle assembly forsupporting data storage disks for rotation about a spindle axis withrespect to a disk drive housing. The assembly includes an elongatespindle shaft, and first and second bushing means at opposite endportions of the spindle shaft. Respective first and second bearing meanssecure the bushing means for rotation relative to the spindle shaft,each bushing means surrounding its respective bearing means.

The first and second bearing means are constructed of a steel, and thefirst and second bushing means are constructed of aluminum, which has acoefficient of thermal expansion greater than the thermal expansioncoefficient of steel. Each of the bearing means is retained in acompression fit within its associated bushing means up to apredetermined maximum temperature.

Preferably the bearing assemblies and the bushing means aresubstantially symmetrical about the spindle axis of the shaft. Becausethe elastic modulus of aluminum is substantially less than that of steel(approximately one-third), the increase in compression about the bearingat lower temperatures tends to cause elastic expansion of the aluminumbushing means rather than elastic contraction of the bearing.Conversely, at higher operating temperatures, the compression fit isretained, although reduced due to the relatively greater expansion ofaluminum (as compared to steel) responsive to the temperature increase.A further advantage of the assembly is that one of the bearing means ismounted to slide axially with respect to the spindle shaft. Axialmovement of the selected bearing means and its associated bushing meansenables an axial retraction of the spindle for convenient assembly intoa unitary deck or other housing structure. This feature also providesaxial adjustment, to eliminate what otherwise would be excessivelystrict tolerances between the mating parts.

A further improvement in the spindle assembly involves means forrestricting the radial passage of air between the first bushing meansand a hub secured to the spindle, and between the second bushing meansand the hub. The restricting means includes a first annular flangeextended axially from either the first bushing means or the hub, into anannular groove provided in the other of the first bushing means and hub.A similar flange and surrounding groove are provided at the interface ofthe second bushing means and hub. In connection with the bushing meansthat is movable axially relative to the hub, the groove and flange areprovided in sufficient length to maintain the flange within itsassociated groove, even with the axially movable bushing means extended.The restricting means further include portions of the first and secondbushing means that extend radially inward along their associated bearingmeans to define a gap between each bushing means and its associatedbearing means. Each gap is open in the radially inward direction to thespindle shaft, and closed in the radially outward direction to form atrap for airborne particulates.

For further improving disk drive performance, the spindle hub can beformed with alternating elongate, axially extended projections andflutes, with the projections supporting disks and intermediate annularspacers. The flutes, in combination with notches or other openingsformed in the spacers and coincident with the flutes, provide passagesfor air radially outward between adjacent disks which, in combinationwith appropriate filtering means, purges the air in the region of thedisks.

Yet another aspect of the present the invention is the aforementioneddeck in combination with a spindle having an elongate spindle shaft,first and second bushing means mounted rotatably at opposite endportions of the spindle shaft and conforming in their profile to therespective precision bores. At least one of the bushing means isslidable axially on the spindle shaft between a recessed position topermit insertion of the spindle assembly into the chamber, and anextended position wherein the first and second bushing means arerespectively inserted into the first and second bores. A hub secures atleast one data storage disk for rotation with the spindle shaft. Firstand second fastening means respectively urge the first and secondbushing means axially away from one another and into a press fitengagement in the first and second bores, to integrally secure thebushing means to the deck while aligning the shaft, hub and disk forrotation relative to the deck and bushing means.

Preferably each of the bushing means includes a substantially flat andaxially outward facing shoulder, and an alignment projection extendedaxially beyond the shoulder. Each alignment projection is insertedwithin its associated bore, with the shoulder abutting the associatedsupport wall surface at the region about the bore. Each of the alignmentsections projects axially outward of its associated shoulder by adistance of less than 0.04 inches. This minimal axial distance,preferably 0.02 inches, adequately retains the projection within itsassociated bore in a compression fit, yet minimizes undesirable scoringor galling, a particularly useful feature in connection with bushingsand deck walls constructed of aluminum. The short projections furtherminimize the potential for harm due to an initial non-perpendicularinsertion of the bushings into the precision bores.

Thus, in accordance with the present invention a variety of novelfeatures are combined to substantially improve the performance of amagnetic disk drive in terms of rigidity, resistance to vibration,resistance to thermal effects and effective sealing against and purgingof aerosols, particles and other contamination. The unitary deck andprecision bores, in combination with the axially retractable spindleassembly, facilitate manufacturing in that alignment and assembly of thespindle shaft into the deck are accomplished simultaneously, and withoutjigs or other extraneous alignment apparatus.

IN THE DRAWINGS

For a further appreciation of the above and other features andadvantages, reference is made to the following detailed description andto drawings, in which:

FIG. 1 is an end view of a magnetic disk drive constructed in accordancewith the present invention, with a cover of the drive housing removed toexpose a spindle assembly and rotary actuator mounted within a deck;

FIG. 2 is perspective view of the drive housing including the deck andcover;

FIG. 3 is a sectional view of the deck taken along the line 3--3 in FIG.1 and with the spindle assembly removed;

FIG. 4 is a partial view of the bottom of the deck;

FIG. 5 is a perspective view of a connector employed with the spindleassembly;

FIG. 6 is a perspective view of the spindle assembly, inverted to showcertain features at the bottom of the assembly;

FIG. 7 is a sectional view of the spindle assembly taken along the line3--3 in FIG. 1;

FIG. 8 is an enlarged partial view of the top of the spindle assembly;

FIG. 9 is an enlarged partial sectional view of the bottom of thespindle assembly;

FIG. 10 is a further enlarged partial view of the top of the spindleassembly;

FIG. 11 is a view of the spindle assembly in the retracted position;

FIG. 12 is a further enlarged partial view of the bottom of the spindleassembly;

FIG. 13 is a partial view of a lower portion of the spindle assembly;and

FIGS. 14-16 illustrate an annular spacer and an adjacent pair of disksof the spindle assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawings, there is shown in FIG. 1 a magnetic diskdrive 16 including a deck 18 forming part of the housing of the drive. Acover is removed from the deck in this figure, to reveal a disk pack 20and a rotary actuator 22, both of which are mounted movably with respectto the deck.

The deck is unitary and preferably constructed of aluminum, and includessubstantially parallel and spaced apart upper and lower support walls 24and 26 which support the disk pack and rotary actuator. The deck furtherincludes opposite side walls 28 and 30, and a rearward wall 32, whichmaintain the spaced apart relation of support walls 24 and 26. Forwardedges of the support walls and side walls form a substantially planarforward edge surface 34, which mates with a conforming edge surface ofthe cover when the cover and deck are joined to form the housing.

Disk pack 20 includes a plurality of disks 36 mounted in coaxial andspaced apart relation to one another on a spindle assembly 38. Thespindle assembly includes an upright spindle shaft 40 (FIG. 7) rotatableon a spindle axis, a hub 42 fixed to the shaft, and a clamping ring 44releasably secured to the bottom of the hub. Clamping ring 44, incooperation with a flange 46 at the top of the hub, clamps disks 36 anda series of annular spacers 48 in an alternating sequence to set theaxial spacing between adjacent disks. Fasteners secure the clamp to thehub, so that the clamp and flange frictionally maintain the disks andspacers integrally with the hub for rotation with shaft 40 about thespindle axis.

In front of hub 42, portions of the disks and spacers in FIG. 1 areremoved to reveal the contour of the hub surface, more particularly aseries of alternating projections 50 and flutes 52 arrangedsubstantially symmetrically about the hub. Projections 50 extendradially outward and have rounded radially outward surfaces thatdirectly engage the disks and spacers, and thus cooperate to support thedisks and spacers. Flutes 52 are recessed radially as compared to theprojections, and provide conduits for air to create a purging air flowas is later explained. A vertical post or column 53 is secured to uppersupport wall 24 and lower support wall 26 by screws or other suitablefasteners. Column 53 is positioned radially outwardly of disks 36, andbeyond the range of arcuate travel of rotary actuator 22, as illustratedin broken lines in FIG. 4. Column 53 rigidifies deck 22, reduces elasticdeformation of the deck in response to the powerful actuator magnet(shown at 55), and raises the natural frequency of the deck for reducedvibration amplitudes.

Rotary actuator 22 includes an actuator shaft 54 mounted to rotaterelative to the deck about a rotary shaft axis. Fixed to the shaft forrotation along with the shaft is an actuator body 56 and a plurality ofhead/arm assemblies 58, each including a magnetic data transducing head60. In a well known manner, rotary actuator 22 is rotatable toselectively position heads 60 with respect to disks 36 for selectivereading and recording of data on the disks.

Deck 18 is shown in greater detail in FIG. 2, along with a cover 62 thatconnects with the deck to provide the disk drive housing. Formed throughupper support wall 24 are a precision bore 64 for accommodating thespindle assembly, and a 15 second precision bore 66 to accommodate ashaft of rotary actuator 22. Four openings at 68 near precision bore 64accommodate fasteners 70 (e.g. socket head screws) used in securingspindle assembly 38 to deck 18. Between two of openings 68 is arectangular slot 72, which accommodates a rigid electrical connectorused in connection with a motor that drives the spindle assembly. A pairof openings 74 and 76 near precision bore 66 accommodate L-shapedactuator stops (not shown), that limit the angular travel of theactuator shaft.

As seen in FIG. 4, a precision bore 78 is formed through lower supportwall 26, concentrically aligned with precision bore 64. Four openings 80about bore 78 accommodate fasteners that secure the spindle assembly. Aprecision bore 82 also was formed through the lower support wall,concentric with bore 66 to accommodate the rotary actuator shaft.

Cover 62 includes parallel and opposed upper and lower walls 84 and 86joined to opposed side walls 88 and 90 and a forward wall 92, togetherforming a unitary cover, like the deck preferably of aluminum. Sidewalls 88 and 90 and upper and lower walls 84 and 86 have rearward edgesthat cooperate to form an edge surface 94 conforming to edge surface 34of the deck. While not illustrated, a recessed gasket generallyconforming to edge surfaces 34 and 94 is maintained between the edgesurfaces when the deck and cover are joined, to provide a fluid seal.

Two series of mutually perpendicular ribs on the deck, indicatedrespectively at 96 and 98, are formed along the exterior of uppersupport wall 24. Similar ribs are formed on the exterior of lowersupport wall 26. Likewise, cover 62 is provided with series ofperpendicular ribs at 100 and 102, with similar ribs on the exterior oflower wall 86. These ribs resist bending and torsional stresses appliedto the deck and cover, to rigidify the disk housing, while permitting apreferred lightweight construction which reduces material cost.

As seen in FIG. 3, upper support wall 24 and lower support wall 26 aretapered, varying from a maximum thickness near bores 64 and 78,respectively, to minimum thickness radially remote from the bores. Asseen in connection with rib 96 and a corresponding rib 104 of the bottomsupport surface, the height of the ribs diminishes in correspondence tothe increasing thickness of the adjacent support wall. The purpose ofthis arrangement is two-fold. First, the maximum thickness providesstrength where it is required most, i.e. proximate the upper and lowerspindle assembly mounting interfaces. Secondly, the tapered walls, asopposed to similarly constructed walls of uniform thickness, moreeffectively attenuate vibration and shock, whereby disk drive 16 issubstantially less subject to damage or impaired performance due tovibrations.

FIG. 5 shows a rigid electrical connector 106, which is inserted intohousing chamber 108 through slot 72 such that pins 110 extend into acorresponding socket of the spindle assembly. Openings 112 at oppositeends of the connector accommodate fasteners turned into openings 114 inthe deck upper support wall. As compared to the flexible connectorpreviously employed between the spindle assembly and the outside of deck18, connector 106 is less subject to damage for lack of carefulhandling, to improve reliability as well as reduce manufacturing cost byreducing the time necessary to form the electrical connections. Thepossibility of damage to the disks from a dangling cable, duringassembly or otherwise, is eliminated.

Spindle assembly 38 is shown in greater detail in FIG. 6 (and invertedin this figure to emphasize certain features at the bottom of thespindle assembly) and FIG. 7. Spindle shaft 40 is not uniform indiameter, but rather is stepped, including upper and lower end portions116 and 118, and upper and lower intermediate shanks 120 and 122. Hub 42is fixed to and surrounds lower shank 122, and abuts a shoulder 124 ofshank 120, which determines the axial position of the hub on the shaft.Hub 42 is aluminum, and formed generally in the shape of a cup, with aradially outward wall 126 extended axially upwardly of the remainder ofthe hub. Hub wall 126 defines a cylindrical cavity containing an annularback iron 128 of steel, and an annular magnet 130 adjacent andsurrounded by the back iron, both being secured integrally to hub 42 torotate with the hub about the spindle axis.

Shaft 40 is supported rotatably by steel ball bearings, including anupper bearing 132 and a lower bearing 134 surrounding upper and lowershaft portions 116 and 118, respectively. An inner race 136 of the upperbearing is mounted slidably along upper shaft portion 116, and biaseddownwardly as viewed in FIG. 8 by an annular spring 138 between bearing132 and a snap ring 140 on the upper end of the spindle shaft. An innerrace 142 of lower bearing 134 is fixed to the spindle shaft at lowerportion 118 using an adhesive and a press fit. Grooves 144 formedconcentrically about the shaft enhance the adhesion of the bearing innerrace.

The outer races of the bearings are contained within respective bushingsin the form of sleeves. More particularly, an outer race 146 of upperbearing 132 is surrounded by an upper sleeve 148, a narrowed portion ofwhich surrounds upper shank 120 of the spindle shaft. Sleeve 148 issecured to outer race 146, but spaced apart a slight distance from theupper shank to permit rotation of spindle shaft 40 relative to sleeve148. One of four openings that extend axially into sleeve 148 is shownat 150. Openings 150 accommodate fasteners 70 through openings 68 in theupper support wall, to secure sleeve 148 integrally with deck 18. Anannular printed circuit 152 is supported on sleeve 148, and a socket 154integral with the printed circuit receives pins 110 of connector 106 forelectrically connecting the spindle assembly with the environmentoutside of deck 18.

A stator, including core laminations 156 and windings 158, surrounds andis fixed to upper sleeve 148. A narrow radial gap between laminations156 and magnet 130 provides clearance for rotation of the magnet and hubrelative to the stationary stator.

A lower sleeve 160 is fixed to an outer race 162 of bearing 134 andsurrounds the bearing. Fasteners through openings 80 in lower supportwall 26 are received into lower sleeve 160, thus to secure the lowersleeve integrally to the lower support wall.

An upper portion of the spindle assembly is enlarged in FIG. 8 to moreclearly show that upper sleeve 148 includes a relatively flat radiallyoutward shoulder 164, and a cylindrical projection 166 axially outwardlyof the shoulder, and conforming in transverse (radial) profile toprecision bore for a nesting, press fit engagement into the bore 64.Projection 166 extends axially away from shoulder 164 by a preferreddistance of about twenty thousandths of an inch, although having alength somewhat greater than 0.020 inches. Likewise, it is seen in FIG.9 that lower sleeve 160 includes a shoulder 170 and a projection 172,extending in the axially outward direction from the shoulder a distanceof at least 0.020 inches. Projection 172 conforms to the shape ofprecision bore 78, again to afford a precise nesting or press fitengagement of the projection into the bore.

As previously noted, upper bearing 132 is mounted slidably on upperportion 116 of the spindle shaft. As seen in FIG. 10, spring 138 isformed of four spring or Belville washers 174, 176, 178 and 180 with aradially inward end portion of washer 174 abutting snap ring 140, and aradially inward portion of washer 180 abutting the inner race of bearing132. Thus, spring 138 biases bearing 132 and sleeve 148 downwardly asviewed in FIGS. 8 and 10. In biasing bearing 132 particularly at innerrace 136, spring 138 applies a preload to the bearing. This of coursedepends upon inner race 136 being slidable on shaft 40, while outer race146 is fixed to sleeve 148. There is a further advantage of thisarrangement, however, as compared to fixing the inner race to the shaftand mounting the sleeve to slide along the outer race. In particular,the exterior of spindle 40, as compared to the inside surface of sleeve148, can be machined to substantially greater precision in achieving acylindrical or round surface. Likewise, the inner surface of inner race136 can be finished with greater precision than the outer surface ofouter race 146. Thus the gap between shaft 40 and inner race 136,necessary to permit sliding, can be substantially narrower than would bean alternative gap between outer race 146 and sleeve 148, tosubstantially reduce spindle tilt.

When spindle assembly 38 is free of deck 18, bearing 132 and sleeve 148are moved downwardly by spring 138 until a bottom surface 182 of thesleeve abuts a radially inward annular surface 184 of hub 42, as shownin FIG. 11. Upper bearing 132, particularly inner race 136, isrelatively close to shank 120 of the spindle shaft. In this retractedconfiguration, the distance between upper projection 166 and lowerprojection 172 (i.e. the axial length of the spindle assembly) is lessthan the vertical distance between the respective inside surfaces ofupper and lower support walls 24 and 26. As a result, pre-assembledspindle assembly 38 is conveniently insertable into chamber 108 formedby deck 18, for preliminary positioning between and at leastapproximately concentrically aligned with bores 64 and 78.

With the spindle assembly retracted but inserted for attachment to thedeck, fasteners 70, e.g. socket head screws, are tightened into sleeves148 and 160 through openings 68 and 80, respectively. Tightening thefasteners draws the sleeves axially outward or apart from one another,each into its respective one of bores 64 and 78. As upper sleeve 148 isdrawn into bore 64, it is urged upwardly relative to hub 42, and in turnurges bearing 132 upwardly along shaft upper portion 116, against thebiasing force of spring 138. With this assembly technique, the bores areof course open to chamber 108, but need not extend completely throughrespective support walls 24 and 26.

Upon complete insertion of the sleeves into the bores, a gap 186 isformed between surfaces 182 and 184 as seen in Figure 7, and a gap 188is formed between bearing inner race 136 and upper shank 120 as is bestseen in FIG. 8. Further, upward movement of the bearing inner racecompresses spring 138 between the inner race and snap ring 140, whichprovides a predetermined load upon bearing inner race 136. Thiseffectively provides a predetermined load to both bearings 132 and 134,for a more stable rotation of the spindle shaft, hub and disks.

Rotary actuator 22 (FIG. 1) is mounted to the deck by inserting actuatorshaft 54 into bores 66 and 82, then fixing the shaft onto V-blocks.Bores 66 and 82 in combination with the V-block construction preciselyalign shaft 54 in parallel, spaced apart relation to spindle shaft 40.

As perhaps best seen in FIG. 9, an annular flange 190 extends downwardlyfrom hub 42 into a corresponding annular groove 192 formed in lowersleeve 160. Similarly, an annular flange 194 projects downwardly fromupper sleeve 148 into an annular groove 196 formed in the hub (FIG. 6).In both cases, a slight clearance between the flange and groovefacilitates rotation of hub 42 relative to the upper and lower sleeves.The juncture of each flange and groove forms a tortuous or convolutedpath which inhibits and controls radially outward passage of air. Theflanges within the grooves, and the narrow axial clearance between thehub and sleeves, temporarily direct radially traveling air into asubstantially axial path, which tends to prevent aerosols, particulatesand other foreign matter generated principally at bearings 132 and 134,from traveling outwardly into the region of disks 36.

Further features cooperate with the respective flanges and grooves toprovide respective labyrinth seals. More particularly, FIG. 12 shows alip 193 formed as part of lower sleeve 160 and extended radiallyinwardly of the remainder of the sleeve, past the gap between inner race142 and outer race 162, and terminating near lower shank 122 of thespindle shaft. Lip 193 is slightly spaced apart from hub 42, and bearing134 by a ledge 191, to form respective horizontal gaps that accommodaterotation of hub 42, spindle 40 and inner race 142 relative to sleeve160. The gaps allow passage of air, and any airborne particulates.However, due to centrifugal force effects during hub and spindlerotation, air and particles tend to flow radially outwardly along thelip and outer race, into a trap or pocket 195. The only alternative pathfor air and particulates is radially inward to the spindle, axiallyupwardly along the spindle, then radially outward and around flange 190.

Corresponding features at the upper end of the spindle assembly are bestseen in FIG. 8. Sleeve 148 includes a ledge 197 that abuts outer race146 whereby an inwardly extending portion 199 of the sleeve is separatedfrom bearing 132 by a narrow, radial or horizontal gap. Portion 199extends radially inwardly of the gap between outer race 146 and innerrace 136. Again, the tendency of air leaving the gap between the races,when the spindle and hub rotate, is to flow radially outwardly, carryingany particulates into a trap near ledge 197. To flow beyond portion 199,air must travel radially inwardly, downwardly along a narrow (less than0.003 inch) gap between sleeve 148 and spindle shaft 40, and then pastflange 194.

Thus, upper and lower labyrinth seals protect against particulatecontamination of disks 36. Both seals utilize axially extended annularflanges within annular grooves, and reduced vertical or axial clearancebetween the sleeves and their respective adjacent bearings, with thesleeve in each case extended inwardly of the gap between its respectiveinner and outer race. The upper labyrinth seal further involves a closespacing of upper sleeve 148 about the spindle upper shank.

A feature of the present invention is the mounting of bearings 132 and134 Within respective sleeves 148 and 160 in a manner which facilitatesthe preferred use of different metals, specifically steel in thebearings and aluminum in the sleeves. The bearings must be constructedof 52100 steel for strength, hardness and wear resistance. At the sametime, aluminum is desired in the sleeves for its superior ability toconduct heat away from the spindle assembly, and for the press fitengagement into deck 18, also of aluminum, to avoid a thermal mismatchbetween the sleeves and deck. The thermal expansion coefficient ofaluminum is greater than the thermal expansion coefficient of 52100steel (11.1-13.4×10⁻⁶ per degree Fahrenheit, as compared tocorresponding range of 6.4-7.0×10⁻⁶ per degree F for 52100 steel).Accordingly, as disk drive 16 heats during operation, sleeves 148 and160 expand more than their associated bearings. To counteract thiseffect, the sleeves are fastened in a compression fit about theirrespective bearings. Further, the relationship between the outerdiameter of each bearing and the inner diameter of each its associatedsleeve is such that the compression fit is retained to a selectedmaximum temperature substantially above temperatures expected underordinary operating conditions.

At the same time, an unduly tight compression fit upon the bearings mustbe avoided. To this end, sleeves 148 and 160, in the regions nearrespective bearings 132 and 134, are sufficiently thin such that thestrain due to compression fit forces is experienced principally by thesleeves. Further ensuring that the sleeves experience most of thisstrain is the fact that the elastic modulus of aluminum is approximatelyone-third that of steel (9.9-11.4×10⁻⁶ psi, as compared to approximately28-30×10⁻⁶ for steel).

Another feature of spindle assembly 38 that counters thermal mismatch isthe manner in which back iron 128 is mounted to hub 42, as seen in FIG.13. A fastener 198, e.g. a socket head screw, is turned into back iron128 through an opening in the hub. A spacer 200 separates back iron 128and magnet 130 from hub 42. Three such pairs of fasteners and spacers,spaced axially apart from one another 120°, secure the back iron. Also,fasteners 198 position back iron 128 to form a radial gap 201 betweenthe back iron and hub 42. This manner of mounting tends to isolate theback iron and aluminum hub from one another, against unwantedinteraction due to thermal effects.

FIGS. 14-16 illustrate the manner in which annular spacers 48, incombination with flutes 52, provide a path for the flow of air duringrotation of the disks and hub. More particularly, a series of notches202 are formed in each of annular spacers 48, and the spacers aremounted on hub 42 to align the notches with flutes 52. Accordingly, asthe rotating disks 36 tend to draw air radially outward, replacement airfrom flutes 52 flows radially outward into the space between each pairof adjacent disks.

As seen in FIG. 1, flutes 52 extend axially and are tapered, in thateach flute progressively narrows in the axially upward direction.Adjacent projections 50 diverge upwardly. Further, a is best seen inFIG. 7, the depth of each flute decreases in the axially upwarddirection. Thus, the air flow capacity of each flute diminishes in theupward direction, which provides an air flow pattern in which air entersthe flutes at the bottom of hub 42, and then proceeds upwardly in theflutes s well as radially outwardly between the disks, for convectioncooling as well as purging. While this arrangement is preferred, it iswithin the scope of the invention to provide diminishing air flowcapacity in the opposite direction for a downward and outward flow ofair, or to provide flutes that converge toward the center of the hub, toreceive air at both ends of the hub for subsequent radially outward flowintermediate the two ends.

Thus, in accordance with the present invention a disk drive is providedthat is easier and less costly to assemble, yet is sturdy, lighterweight and reliable in its operation. The axially retractable spindle,in combination with precision bores in the deck, permits precisemounting of the spindle assembly directly into the deck, without theneed for jigs or other extraneous tooling for proper alignment. The useof a continuous, unitary deck to support both the spindle shaft and therotary actuator shaft ensures a precise alignment of the actuator andspindle assembly, and eliminates any effect of thermal mismatch orfailure to precisely connect separate parts of the disk drive housing.Finally, the flow of purging air through the hub flutes, and thelabyrinth seal protecting the disk region from the internal bearing andmotor areas of the spindle, combine to significantly enhance long termoperation of the drive.

What is claimed is:
 1. A spindle assembly for supporting data storagedisks for rotation relative to a fixed housing, including:an elongatespindle shaft having a spindle axis; a generally cup-shaped spindle hubhaving a first portion secured to the spindle shaft and an annular wallextended axially from the first portion for supporting at least one datastorage disk for rotation about the spindle axis, said annular wallsurrounding the spindle shaft and substantially concentric on thespindle axis; an annular back iron having an annular edge, and aplurality of fasteners extended through the first portion and into theback iron through the annular edge, for securing the back ironintegrally with respect to the hub and substantially concentric on thespindle axis; and a plurality of spacers between the annular edge of theback iron and the hub, each spacer proximate an associated one of thefasteners, for maintaining the hub and annular edge of the back iron inaxially spaced apart relation.
 2. The spindle assembly of claim 1wherein:Each of said spacers surrounds its associated fastener.
 3. Aspindle assembly for supporting data storage disks for rotation relativeto a fixed housing, including:an elongate spindle shaft having a spindleaxis; a generally cup-shaped spindle hub including a first portionsecured to the spindle shaft and an annular wall extended axially fromthe first portion for supporting at least one data storage disk forrotation about the spindle axis, said annular wall surrounding thespindle shaft substantially centered on the spindle axis; an annularback iron having an annular edge, a plurality of fasteners extendedaxially through the first portion and into the back iron through theannular edge, for securing the back iron integrally with respect to thehub, and a spacing means between the hub and the annular edge, formaintaining the annular edge of the back iron in axially spaced apartrelation to the first portion of the hub.
 4. The spindle assembly ofclaim 3 wherein:said spacing means includes a plurality of spacers, onespacer surrounding each of the fasteners.
 5. The spindle assembly ofclaim 4 wherein:said fasteners mount the annular back iron in spacedapart relation to the annular wall of the hub to define a radial gapbetween the hub and the back iron.
 6. The spindle assembly of claim 5further including: stationary first and second bushings, a first bearingmeans for mounting a first end of the spindle shaft to the first bushingfor rotation of the spindle about the spindle axis, and a second bearingmeans for mounting a second and opposite end of the spindle shaftrelative to the second bushing for rotation about the spindle axis, saidspindle hub being integrally secured to the spindle shaft for rotationwith the shaft.
 7. A spindle assembly for supporting data storage disksfor rotation relative to a fixed housing, including:an elongated spindleshaft rotatable on a spindle axis; a hub secured integrally to thespindle shaft and supporting at least one data storage disk for rotationwith the spindle shaft; a stationary first bushing and a first bearingmeans for mounting a first end of the spindle shaft to rotate relativeto the first bushing about the spindle axis, said first bearing meanssurrounding the spindle and being surrounded by the first bushing; asecond stationary bushing and a second bearing means for mounting asecond and opposite end of the spindle to rotate about the spindle axisrelative to the second bushing, said second bearing means surroundingthe spindle shaft and being surrounded by the second bushing; whereinthe hub is disposed between the first and second bushings and defines afirst radial gap between the hub and the first bushing, and a secondradial gap between the hub and the second bushing, and wherein each ofthe bushings cooperates with its associated bearing means to preventradially outward passage of air between the bushing and its associatedbearing means; wherein the first bushing includes a first flowrestriction means extending radially inward toward the spindle shaft anddisposed between the first bearing means and the hub, said firstrestriction means terminating proximate the spindle shaft to define afirst axial gap for accommodating passage of air between the firstbearing means and the first radial gap; and wherein the second bushingincludes a second flow restriction means extended radially inwardbetween the second bearing and the hub, and terminating proximate thespindle shaft to define a second axial gap to accommodate passage of airbetween the second bearing means and the second radial gap.
 8. Thespindle assembly of claim 7 wherein:each of the bearing means has aninner race surrounding the spindle shaft and an outer race surroundingthe inner race, and each of the flow restriction means extends radiallyinward at least to the associated inner race.
 9. The spindle assembly ofclaim 7 further including:an annular first flange extended axially fromone of the first bushing and the hub, toward the other of the firstbushing and the hub, and an annular first channel in said other of thebushing means and hub, opposite the annular first flange and surroundingthe annular first flange in non-contacting relation thereto; and anannular second flange extended axially from one of the second bushingand the hub, toward the other of the second bushing and hub, and anannular second channel in said other of the second bushing and hub,opposite the annular second flange and surrounding the second flange innon-contacting relation thereto.
 10. The spindle assembly of claim 9wherein:at least one of the first and second bushing is moveable axiallyrelative to the hub and spindle shaft between proximate and remotepositions with respect to the hub, and wherein the annular flange andthe annular channel corresponding to the selected bushing means and hubeach have an axial length sufficient for containment of the annularflange within the associated annular channel when the selected bushingmeans is in the remote position.
 11. The spindle assembly of claim 9further including:an annular back iron concentric on the spindle axis, aplurality of fasteners for securing the back iron integrally withrespect to the hub, and a plurality of spacers, one surrounding each ofthe fasteners, for maintaining the back iron axially spaced apart fromthe hub.
 12. The spindle assembly of claim 11 wherein:the hub iscup-shaped and has an annular radially outward wall concentric on thespindle axis, and the back iron is mounted to the hub in radially spacedapart relation to the annular radially outward wall.
 13. The spindleassembly of claim 8 wherein:the inner race of a selected one of thefirst and second bearing means is mounted to slide axially with respectto the spindle shaft, to enable axial movement of the selected bearingmeans and its associated bushing with respect to the spindle shaft andthe hub.
 14. The spindle assembly of claim 13 further including: abiasing means on the spindle shaft to urge the inner race of theselected bearing means in the axial direction toward the other bearingmeans.